Present telecommunication systems such as the Public Switched Telephone Network, PSTN, the Integrated Services Digital Network, ISDN, mobile telecommunication systems and Internet Protocol, IP, communication systems like the Internet protocol Multimedia Subsystem, IMS, and Voice over IP, VoIP, systems provide a service to a called or receiving party for identifying a calling or originating party on the basis of a directory number or Calling Line Identity, CLI.
With this service, during set up of a communication by a calling party, an identity of the calling party, such as his/her user or subscriber number, is transmitted towards the User Equipment, UE, of the called party. The called party receives an indication on the display of his/her UE about the identity of the calling party, such as the user or subscriber number or other information associated with a user or subscriber number and stored in a memory of the UE, such as the name of the calling party, for example.
However, in some cases, users do not wish to be identified, for example unlisted users having their subscriber number not listed in public phone directories or the like. To that end, a service called Calling Line Identification Restriction, CLIR, is available in the telecommunication systems. With this service the identity of a calling party is withheld from a called party, such that the called party will not receive information concerning the identity of a calling party. With CLIR enabled, a server or node of the telecommunication network indicates the restriction of the calling party identity towards a further node of the telecommunication network by including a privacy flag in the signalling information when establishing communication. As a result of this flag, the calling party identity is suppressed and not displayed on the UE of the called party, such that the calling party remains anonymous to the called party.
A selected and restricted group of users comprising emergency services, police and law enforcement agencies and the like may be authorised to use a service called CLIR-override. With CLIR-override the calling party identity can be retrieved to the called party, even if CLIR is enabled for the calling party. This service, however, is not generally available for users or subscribers of a telecommunication system but only through special permission.
In general, when CLIR is enabled, the calling party may not want to be called back or be reachable on a public number. However, in some cases it would be desirable to call back, for example when a call is dropped or when the called party needs to contact the calling party. Another situation in which call back would be desirable is the case in which the called party has missed the call, i.e. a no answer condition.
In practice there is a service available for calling back user or subscriber numbers, wherein dialling a particular string, such as *69, by a called party, results in calling back, by the telecommunication system, of the calling party involved with the most recent call, even when the CLI of that party is restricted.
A service called Automatic Recall, which is an implementation of the ISDN standard, is built around the same principle. With Automatic Recall a called party can retrieve the user or subscriber number of the calling party of the last call received by the called party as well as a time stamp of that call. The service also provides the called party the choice of calling back on this most recent call. However, when a privacy flag such as CLIR is enabled for the calling party, the identity of the calling party is withheld for the called party. Despite that, the Automatic Recall service is capable of re-establishing the communication between the called party and the calling party of the most recent incoming call.
These prior art services, however, have several drawbacks, in that they only allow for calling back the last or most recent, incoming call. For example, if between receiving a call from a party calling with a withheld identity and the time of calling back that party the called party is faced with an additional incoming call, the possibility of calling back the called party with the withheld identity is lost.
Further, there is no possibility of establishing communication with an anonymous calling party from a communication device other than the UE that received a call from the anonymous calling party. Other forms of communication may, likewise, not be possible such as sending an e-mail or text or multimedia message when receiving a telephone call of a calling party with a withheld identity, for example.